Biometry is used to determine axial length of the eye and
to determine the depth of the anterior chamber, lens and vitreous cavity. The
A-scan ultrasound is the most commonly employed, since it is an essential part
of the preoperative evaluation of cataract surgery patients. It is used to
determine the appropriate dioptric power of the intraocular lens (IOL) implanted
at the time of cataract extraction surgery. This allows the correct selection of
an intraocular lens (IOL) implant through a series of
calculations. The A-scan technique takes multiple, accurate readings on both
eyes.